Various studies have been done on binocular display apparatuses and their applications. For example, their applications as vision aid systems for the visually impaired have been studied. Common causes of vision disorders include eye diseases, such as glaucoma, cataract, night blindness, and age-related macular degeneration, and developmental disorders, such as vision disorders in childhood. As remedies, various aid cameras and aid displays have been proposed. In this context, binocular display apparatuses are employed as aid displays. As one example, there is proposed a goggle-type vision enhancement device in which an image in a region corresponding to a user's visual field out of a picture taken with a CCD camera is subjected to image processing for viewing by the user through a virtual-image display device (Patent Document 1). For another example, there is proposed a configuration in which image information obtained from an imager is processed to be displayed in a display area on a display such that, on the display, a user can see the processed image in the display area simultaneously with an image of the outside world (Patent Document 2).